FIELD OF THE INVENTION
The present invention generally relates to a control system of electrostatic
precipitator used for air pollution control. In particular, the invention relates to
an apparatus for controlling energisation of electrostatic precipitator. More
particularly, the invention relates to a versatile apparatus for controlling low,
medium and high frequency high voltage power systems for energisation of
electrostatic precipitator.
BACKGROUND OF THE INVENTION
Electrostatic precipitation is one of the most effective processes to control air
pollution generated by industrial emissions. This technique, which has proved to
be highly effective in controlling air pollution, is used for removal of undesirable
matter from a gas stream by electrostatic precipitation. Electrostatic precipitator
(hereafter referred to as ESP) is an air pollution control device designed to
electrically charge and collect particulates generated from industrial processes
such as those occurring in power plants, cement plants, pulp and paper mills and
utilities. Electrostatic dust removing basic working principle is that: when the
dust ladden gas flow through the high-voltage static electric field inside ESP,
dust is charged due to collisions with positive and negative ion, under the action
of the electric field the charged dust particle moves to opposite charged
electrode plates, viz., discharge electrode and collection plate, and eventually
gets adsorbed, thus achieving dust-collecting effect. ESP is divided into a
plurality of fields depending on the dust load. During continuous operation of an
electrostatic precipitator, the dust from the collector plates and the discharge
electrodes must be periodically removed for further conveying of the collected

dust. Dust collected on the electrodes is removed by periodically rapping/hitting
the electrodes with mechanical hammers controlled by rapping motors. The
rapping mechanism is critical to ESP efficiency and so is automatically controlled
either through a dedicated controller or by the controller of ESP Power supply
itself.
In the ESP, the efficiency of the system mainly depends on energisation of ESP
fields. An ESP installation consists of a plurality of fields, each field being
individually energised. The ESP fields are arranged in pass-wise along the gas
flow direction.
The most widely known energisation technique of ESP is by using a single-phase
mains frequency silicon phase-controlled power supply. Then came the three-
phase power frequency silicon controlled rectifier power supply. The latest prior
art being the Insulated Gate Bipolar Transistor (hereafter referred as IGBT)
controlled high frequency high voltage Switch Mode Power Supply (hereafter
referred as SMPS). All these three power supply systems for ESP are having its
own advantages and disadvantages and the selection of power supply system
vary from case to case. Each of these systems have its own control system for
optimum operation and monitoring and requires dedicated controllers to cater to
the specific control and monitoring inputs and outputs of each of the three typed
of known power supply systems for ESP.
In the prior art, electronic controllers (hereafter referred as EC) exist to control
the thyristor based line frequency linear power supply systems of ESP. They are
meant only for that particular system and hence cannot be used to control a 3
phase power supply system or a high frequency (> line frequency) SMPS system
for ESP energisation. Similarly, there exist dedicated ECs for 3 phase power
supply and for SMPS system.

The prior art for example, CN102755931 A, and CN202410836U, teach variable
frequency (50 - 400 Hz) IGBT based SMPS system for ESP with a Digital Signal
Processor (hereafter referred as DSP) based controller. It has provisions for
Controller Area Network (hereafter referred as CAN) protocol based
communication. But the controller doesn't have provisions for controlling line
frequency linear power supplies and capable of operating in a limited range of
50 to 400 Hz. The controller doesn't have provision for inbuilt rapping system
control and heater control.
Prior patent publications for examples US8233255B1 and WO2013056406A1
disclose three phase high frequency IGBT based SMPS system for ESP
energisation. The EC is capable of monitoring and controlling the rectifiers, IGBT
inverters, switching frequency, charging etc. But the EC doesnot have provisions
for controlling line frequency linear power supplies. The EC is not having any DSP
for faster operation of the IGBT switching circuits. EC doesnot have any CAN
communication for remote monitoring and control. Also, the EC doesnot come
with in-built rapping system control.
Indian patent, no:233655 (491/KOL72005) discloses an EC for ESP with CAN
communication for peer to peer communication and remote monitoring and
control. The EC also has provisions of in-built rapping control also. But the EC is
designed only for control of line frequency thyristor based linear power supply. It
lacks the capability to control high frequency high voltage SMPS systems for ESP
energisation.
Accordingly, the prior art fail to disclose a versatile apparatus which can cater for
controlling line frequency single phase systems, three phase thyristor controlled

power supply systems, and medium and high frequency IGBT based SMPS
systems for ESP.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a versatile apparatus for
controlling line frequency single phase systems, three phase thyristor controlled
power supply systems and medium and high frequency IGBT based SMPS
systems for electrostatic precipitator, which eliminates the need for providing
separate controllers for auxiliary systems.
Another object of the invention is to propose a versatile apparatus for controlling
line frequency single phase systems, three phase thyristor controlled power
supply systems and medium and high frequency IGBT based SMPS systems for
electrostatic precipitator, which is capable of controlling/switching at a wide
frequency range (500 - 10000 Hz) the high voltage SMPS system. This will
provide a great flexibility in selection of power supply system
A still another object of the invention is to propose a versatile apparatus for
controlling line frequency single phase systems, three phase thyristor controlled
power supply systems and medium and high frequency IGBT based SMPS
systems for electrostatic precipitator, which has in-built rapping and heater
control and avoids an extra control system for rapping and heating operations of
the ESP.

Yet another object of the invention is to propose a versatile apparatus for
controlling line frequency single phase systems, three phase thyristor controlled
power supply systems and medium and high frequency IGBT based SMPS
systems for electrostatic precipitator, which is based on DSP and allows for faster
operation.
A further object of the invention is to propose a versatile apparatus for
controlling line frequency single phase systems, three phase thyristor controlled
power supply systems and medium and high frequency IGBT based SMPS
systems for electrostatic precipitator, which is enabled to operate CAN-based
multi master communication protocol for remote monitoring and control.
A still further object of the invention is to propose a versatile apparatus for
controlling line frequency single phase systems, three phase thyristor controlled
power supply systems and medium and high frequency IGBT based SMPS
systems for electrostatic precipitator, which reduced the maintenance cost of the
ESP.
SUMMARY OF THE INVENTION
Accordingly, there is provided a versatile apparatus for controlling line frequency
single phase systems, three phase thyristor controlled power supply systems
and medium and high frequency IGBT based SMPS systems for electrostatic
precipitator.

As per the invention, the apparatus comprises a first hardware structure with
associated software for controlling ESP energisation, spark/arc detection and
quenching, back corona detection and suppression; a second hardware structure
with associated software for controlling each phases separately for a three phase
power supply system for ESP; a third hardware structure with associated
software for generating PWM signals to control the IGBT inverter in an SMPS
system, including adjustment of switching frequency of inverter system for a
wide range (500 - 10000 Hz); a fourth hardware structure with associated
software to control the rectifier part of SMPS system; a fifth hardware structure
with associated software for initiating control action based on output parameters
from the ESP in the form of current and voltage, intermediate stage DC bus
voltage and current ;and a multi master protocol based CAN communication
network for peer to peer communication including remote monitoring and
control, wherein the apparatus is further enabled to perform control and
monitoring of rapping motors including heaters.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 is hardware block diagram of a versatile control apparatus of the ESP,
according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The versatile apparatus (Electronic Controller (EC)) of the invention receives the
feedback signals and executes methods to control line frequency single phase
and three phase thyristor controlled power supply systems and medium and high
frequency IGBT based SMPS systems for ESP. as shown in Fig. 1.

In Fig. 1, block (8) is a power supply unit for the EC which interalia provides
power for the controller and peripheral devices.
In Fig. 1, block (1) is a central processor (DSP) which executes the software
methods for feedback control of the ESP. It has provisions to take analog and
digital signals as feedback signals. It has provisions to output control signals
based on input signals for controlling the ESP. It has inbuilt memory to store the
program (control logic). It executes methods to implement a feedback control
for ESP energisation, spark/arc detection and quenching, back corona detection
and suppression based on ESP voltage and current parameters as feedback. It
has the provision to generate PWM signals for firing the thyristors and for
switching the IGBTs. It has provisions to take status feedback from rapping
motors and heaters and it executes the software methods for controlling the
rapping and heater operations. It has inbuilt CAN communication module for
remote monitoring and control through a multi master communication network.
In Fig. 1, block (2) is an interface for coupling the PWM firing control pulses
from a microcontroller to the thyristors, including PWM switching pulses to the
IGBT driver circuit. Power supplied to the ESP depends on firing of the thyristors
and switching of thelGBTs.
In Fig. 1, block (3) is an interface connecting the feedback signals (ESP current
and voltage, DC bus voltage and current before inverter) from the EC panel to
the DSP.

In Fig. 1, block (4) is an interface connecting different alarm signals
(Transformer alarms, overloads, fault indications etc) coming from the power
supply system for ESP to the DSP(l).
In Fig. 1, block (5) is an interface for coupling the rapping motor and heater
status signals from the corresponding systems to the DSP(l) of the EC. It also
couples the ON/OFF commands from the DSP to the rapping motors and heaters.
In Fig. 1, block (6) is a standard JTAG interface for loading the software into the
inbuilt memory of the DSP.
In Fig. 1, block (7) is a CAN communication interface for connecting the EC with
an user interface including a CAN-based communication network for remote
monitoring and control system.

WE CLAIM :
1. A versatile apparatus for controlling low, medium and high frequency high
voltage power systems for energisation of electrostatic precipitator, comprising:
a first hardware structure with associated software for controlling ESP
energisation, spark/arc detection and quenching, back corona detection and
suppression;
a second hardware structure with associated software for controlling each
phases separately for a three phase power supply system for ESP;
a third hardware structure with associated software for generating PWM signals
to control the IGBT inverter in an SMPS system, including adjustment of
switching frequency of inverter system for a wide range (500 - 10000 Hz);
a fourth hardware structure with associated software to control the rectifier part
of SMPS system;
a fifth hardware structure with associated software for initiating control action
based on output parameters from the ESP in the form of current and voltage,
intermediate stage DC bus voltage and current ;and
a multi master protocol based CAN communication network for peer to peer
communication including remote monitoring and control, wherein the apparatus
is further enabled to perform control and monitoring of rapping motors including
heaters.
2. The apparatus as claimed in claim 1, wherein the central processor/DSP is
provided with in-built control program.

3. The apparatus as claimed in claim 1, wherein the control module is based on
the ESP current feedback signals transmits a firing PWM signal with specific
pulses to fire the back to back connected thyristor pairs of each phase of the
linear power supply.
4. The apparatus claimed in claim 1, wherein the control module is based on the
ESP current feedback signals transmits a firing PWM signal with specific pulses to
switch the IGBT inverter stack of the SMPS system.
5. The apparatus as claimed in claim 1, wherein the central processor/DSP is
programmable to generate PWM pulses for switching the IGBT for a frequency
range of 500 to 10000 Hz.
6. The apparatus as claimed in claim 1, comprising an interface for coupling the
thyristor firing control pulses and IGBT switching pulses from the DSP to the
thyristor pairs and an IGBT inverter stack.
7. The apparatus as claimed in claim 1, comprising an interface for coupling the
secondary feedback signals, alarm signals, DC bus feedbacks, primary input
current and voltage feedbacks to the DSP of the apparatus.
8. The apparatus as claimed in claim 1, wherein the central processor/DSP is
provided with and in-built control program to control and monitor rapping
motors and heaters

9. The apparatus as claimed in claim 1, comprising an interface for coupling the
rapping motor and heater ON/OFF signals from the DSP and the status signals of
the motors and heaters to the DSP.

ABSTRACT

The invention relates to a versatile apparatus for controlling low, medium and
high frequency high voltage power systems for energisation of electrostatic
precipitator, comprising: a first hardware structure with associated software for
controlling ESP energisation, spark/arc detection and quenching, back corona
detection and suppression; a second hardware structure with associated
software for controlling each phases separately for a three phase power supply
system for ESP; a third hardware structure with associated software for
generating PWM signals to control the IGBT inverter in an SMPS system,
including adjustment of switching frequency of inverter system for a wide range
(500 - 10000 Hz); a fourth hardware structure with associated software to
control the rectifier part of SMPS system; a fifth hardware structure with
associated software for initiating control action based on output parameters
from the ESP in the form of current and voltage, intermediate stage DC bus
voltage and current ;and a multi master protocol based CAN communication
network for peer to peer communication including remote monitoring and
control, wherein the apparatus is further enabled to perform control and
monitoring of rapping motors including heaters.